I recently bought a 2 year old condo that had been empty for over a year. The water was shut off which was fine, but the water softener was empty apart from about a foot of dirty water in the bottom. I bailed this out, but what do I do now. Put salt in & hope it works.
Can someone please help.

Yep, make sure tank is as clean as you can get it, add salt and you should be set.

Mygirlsdad77 is right. Clean out the brine tank, make sure that the softener is not by-passed so that water is going into the softener. (look where the pipes go into and out of your softener, there should be either a dial to push in, or valves to open, or a lever to slide) Then once you put the salt in, I would run it through a manual regeneration cycle TWICE. Each one takes about an hour and a half. If you are not sure how to do that tell us what type of softener you have and we can walk you through it.
Hope this helps